Under certain circumstances, blood neutrophils (PMNs) release reactive oxygen metabolites or other agents that cause injury to organs. The possibility that some chemicals produce acute organ toxicity indirectly by stimulating blood PMNs to release oxygen radicals or other injurious substances has not been extensively explored as a general mechanism of toxicity. The overall goal of the proposed research is to characterize the stimulatory effects of certain toxic chemicals on PMNs and to evaluate the importance of PMN stimulation in their acute toxicities. Initial studies will focus on Alpha-naphthylisothiocyanate (ANIT), since its hepatotoxicity is associated with accumulation of PMNs at the site of injury and since we have shown recently that ANIT stimulates rat PMNs to release superoxide radical in vitro. The first series of experiments will be performed using rat PMNs in vitro. The ability of ANIT to stimulate several PMN responses will be examined and concentration/response curves generated. These functional responses will include oxygen radical release, lyosomal enzyme release, PMN aggregation and chemotaxis. In addition, the cytotoxicity of ANIT toward PMNs will be evaluated. If ANIT produces cholestasis and hyperbilirubinemia in vivo its ability to stimulate PMNs, then depletion of blood PMNs should reduce these effects. This will be tested in rats depleted of PMNs by an anti-PMN serum. If release of toxic oxygen radicals by PMNs is responsible for ANIT hepatotoxicity, then pretreatment of rats with agents that scavenge or interfere with formation of oxygen radicals should decrease ANIT's effects. Accordingly, superoxide dismutase, catalase, desferroxamine and dimethylsulfoxide will be tested for their abilities to reduce ANIT hepatotoxicity. These studies in vivo will be supported by related studies in isolated livers, in which the composition of the perfusion medium can be altered to elucidate the role of blood elements. Finally, experiments will be performed to determine (1) if species differences in ANIT toxicity in vivo correlate with ANIT's ability to stimulate PMNs in vitro; (2) if agents that alter ANIT hepatotoxicity also alter effects of ANIT on PMN functions; (3) if Beta-naphthylisothiocyanate, a structurally related compound which does not produce cholestatic liver injury, shares with ANIT the ability to stimulate PMNs. These investigations may uncover a mechanism by which agents that produce "drug-induced" liver injury act. The long-term goal of this research is to determine the extent and nature of the participation of stimulated phagocytic cells in toxic responses to chemicals.